Labyrinth

A labyrinth pattern self assembles as a granular suspension dries out. The material is sandwiched between to glass plates, and fluid is withdrawn through a tube and a hole in the centre of the top plate. Fingers of air sweep up the granular material – glass beads of 100 micrometer average diameter – and produce a simply connected branching labyrinth. The constant spacing between the branches represents a balance between friction and surface tension at the interface. The initial disc is 35 cm across.